Captisol® is a polyanionic beta-cyclodextrin derivative with a sodium sulfonate salt separated from the lipophilic cavity by a butyl ether spacer group, or sulfobutylether (SBE). Captisol® is not a single chemical species, but comprised of a multitude of polymeric structures of varying degrees of substitution and positional/regional isomers dictated and controlled to a uniform pattern by a patented manufacturing process consistently practiced and improved to control impurities.

The selection of Captisol® and its desirable safety profile and drug solubilization properties was based upon extensive evaluations of the mono, tetra and hepta-substituted dominated compositions. Captisol® is the trade name for Ligand's modified beta-cyclodextrin technology.

Several hundred of pre-clinical and clinical studies have been performed and indicate that Captisol® is safe when administered parenterally or orally and does not exhibit the nephrotoxicity associated with beta-cyclodextrin. Relative to beta-cyclodextrin, Captisol® provides higher interaction characteristics and superior water solubility in excess of 100 grams/100 ml – a 50-fold improvement.